Heterologous Expression of Argininosuccinate Synthase From Oenococcus oeni Enhances the Acid Resistance of Lactobacillus plantarum.

Hongyu Zhao,Hua Wang,Longxiang Liu,Lin Yuan,Shuai Peng,Hua Li

doi:10.3389/fmicb.2019.01393

Abstract

Oenococcus oeni can survive well in wine (an acid-stress environment) and dominate malolactic fermentation (MLF). To demonstrate a possible role of argininosuccinate synthase gene (argG) in the acid tolerance response of O. oeni, a related argG gene was inserted into a plasmid pMG36e and heterologously expressed in Lactobacillus plantarum SL09, a wine isolate belonging to a species of relevant importance in MLF. The expression levels of the argG gene in L. plantarum were analyzed by RT-qPCR, argininosuccinate synthase (ASS) activity and cell properties (amino acids, pH, H+-ATPase activity, and ATP levels) were determined at pH 3.7 in comparison with that at pH 6.3. Results showed that the recombinant strain L. plantarum SL09 (pMG36eargG) exhibited stronger growth performance compared with the control strain (without argG gene), and the expression levels of hsp1, cfa, atp, the citrate and malate metabolic genes were apparently increased under acid stress. In addition, the recombinant strain exhibited 11.0-, 2.0-, 1.9-fold higher ASS activity, H+-ATPase activity and intracellular ATP level, compared with the corresponding values for control strain during acid-stresses condition, which may take responsible for the acid tolerance enhancement of the recombinant strain. This is the first work report on heterologous expression of argG gene, and the results presented in this study will be beneficial for the research on acid stress response of O. oeni.

Highlights

Oenococcus oeni, an important lactic acid bacteria (LAB), is critical for winemaking owing to the ability of deacidification and stabilization of wine through malolactic fermentation (Betteridge et al, 2015; Peng et al, 2018; Romero et al, 2018)
The citrate metabolism affects the acid tolerance of O. oeni, owing to its end products (Augagneur et al, 2007), with MargalefCatalà et al (2016) finding that the genes involved in glutamine and glutamate metabolism were upregualted of O. oeni under stress
argininosuccinate synthase (ASS) is considered as the rate-limiting enzyme for arginine biosynthesis (Lemke and Howell, 2002), we observed that the argininosuccinate synthase gene (argG) gene of O. oeni SD-2a was apparently over-expressed after acid shock in our previous research (Liu et al, 2017), and functioned as a core regulatory gene during acid stress response according to its place in a gene co-expression network

Summary

Introduction

Oenococcus oeni, an important lactic acid bacteria (LAB), is critical for winemaking owing to the ability of deacidification and stabilization of wine through malolactic fermentation (Betteridge et al, 2015; Peng et al, 2018; Romero et al, 2018). The optimal pH for O. oeni growth is 4.8–5.5, wine is a harsh environment, with high acidity (pH 3.0–3.5), which is considered as a major stress for O. oeni growth (Fortier et al, 2003; Rosi et al, 2003; Guzzo, 2011). The citrate metabolism affects the acid tolerance of O. oeni, owing to its end products (Augagneur et al, 2007), with MargalefCatalà et al (2016) finding that the genes involved in glutamine and glutamate metabolism were upregualted of O. oeni under stress. ASS is considered as the rate-limiting enzyme for arginine biosynthesis (Lemke and Howell, 2002), we observed that the argG gene of O. oeni SD-2a was apparently over-expressed after acid shock in our previous research (Liu et al, 2017), and functioned as a core regulatory gene during acid stress response according to its place in a gene co-expression network. The potential role of the argG gene on O. oeni acid stress has not been elucidated

Methods

Results

Conclusion